Device and method for automatically detecting installed lamp type

ABSTRACT

An apparatus ( 1100, 2000, 3000 ) executes an algorithm ( 2000 ) to determine a type of lamp ( 10 ) that is installed in a lighting unit ( 1000 ). The apparatus supplies power to the installed lamp ( 10 ) according to a first power control setting that will not overdrive the installed lamp when the installed lamp is of a first lamp type, and that will overdrive the installed lamp when the installed lamp is of a second lamp type. The apparatus ( 1100, 2000, 3000 ) detects whether the installed lamp ( 10 ) is overdriven at the first power control setting, and uses the detection result to determine the lamp type of the installed lamp ( 10 ). The apparatus ( 1100, 2000, 3000 ) then supplies power to the installed lamp ( 10 ) according to the determined lamp type.

TECHNICAL FIELD

The present invention is directed generally to a lighting unit and adevice for supplying power to a lamp in a lighting unit. Moreparticularly, various inventive methods and apparatus disclosed hereinrelate to an arrangement and method for detecting a type of lamp that isinstalled into a lighting unit and for supplying power to the installedlamp according to its type.

BACKGROUND

Certain types of lamps have the same physical configuration as eachother and can be installed in the same lighting unit.

However, in some cases these different lamp types can have differentpower supply requirements. In such cases it is important to be able toidentify the type of lamp that is installed in the lighting unit so thatit can be driven properly.

For example, a T8 lamp is a standard fluorescent lamp having a tubularshape with a diameter of a one inch, a medium bi-pin base, and havingseveral specified lengths, including 2 feet, 3 feet, and 4 feet. As iswell known, a ballast is employed to supply power to drive a T8fluorescent lamp. Among 4 foot T8 lamps, there are several differentlamp types, including a first type of lamp which is a standard 32 wattT8 lamp, a second type of lamp which is an energy saving 28 watt T8lamp, and a third type of lamp which is an energy saving 25 watt T8lamp. All of these types of lamps can be installed in the same lightingfixture that supports a 4 foot T8 lamp, but each of these types of lampshas its own specific power supply requirements.

When a fluorescent lamp such as a T8 lamp is installed in a non-dimmingsystem, the ballast provides a constant current to the lamp. In thatcase, a 25 watt T8 lamp has a lower operating voltage than a 28 watt T8lamp (or a 32 watt T8 lamp) and therefore consumes less power.

However, when it is desired to provide a dimming capability for afluorescent lamp such as a T8 lamp that is installed in a lightingarrangement that employs dimming, a ballast needs to be employed thatsupports a dimming operation. In general, existing dimming ballastsemploy a feedback loop to operate the lamp at a desired setting for thedesired level of dimming. Typically, dimming ballasts have eitherconstant current or constant power control loops to achieve a deepdimming level. If an energy saving lamp is installed on a dimmingballast with a constant power control loop that is designed for a higherpower lamp, especially at higher light output levels where little or nodimming is desired, the ballast will try to overdrive the lamp in orderto satisfy its control loop requirements and therefore the energy savinglamp will not save energy, or will not save as much energy as would beexpected and desired. In that case, when replacing a higher power lamp(e.g., 32 watt T8 lamp) with a lower power lamp (e.g., 28 watt T8 lamp),for example, it may be necessary to install a different ballast to matchthe lower power lamp.

It would be desirable to be able to substitute any one type of theselamps for any other type of these lamps in a particular lighting unitwithout also having to exchange the ballast that drives the lamp. Inthat case, it is desirable to have a lighting unit that canautomatically detect the type of lamp that is installed therein, and toadjust operating parameters of the ballast accordingly, to properlydrive the installed lamp.

Lamp determination in the past has typically used measurements such asfilament resistance, lamp current, and lamp voltage to determine lamptype. This is an effective strategy when lamp characteristics are verydifferent, but can have difficulties when these parameters don't have alarge enough difference. For instance, a standard T8 32W lamp has thesame filament resistance as 28W T8 and 25W T8 energy saving lamps. Lampcurrent is also the same for these lamps. The only difference betweenthem is the lamp voltage, and this voltage can overlap with temperaturechanges and is difficult to measure.

Thus, there is a need in the art to provide an automated method ofdetermining a type of lamp that is installed in a lighting unit. Thereis also a need to provide a device capable of driving a plurality oftypes of lamps, and also capable of automatically detecting the type oflamp which it is currently driving.

SUMMARY

The present disclosure is directed to a system and method for detectinga type of lamp that is installed in a lighting unit. For example, thepresent disclosure describes a dimming ballast and associated controllerfor a fluorescent lamp that can automatically detect the type offluorescent lamp that is installed in a lighting unit associated withthe ballast, where each different fluorescent lamp type is associatedwith a corresponding power level at which the lamp is intended to bedriven.

Generally, in one aspect, a device is provided for supplying power to aninstalled fluorescent lamp. The device comprises: a first circuit forreceiving an input voltage and in response thereto supplying power tothe installed fluorescent lamp, the first circuit including: a halfbridge having first and second switches that are selectively turned onand off periodically, wherein each switch has a time T_(ON) in eachperiod where the switch is turned on, and wherein the power levelsupplied to the installed fluorescent lamp varies with T_(ON), and aresonant circuit for supplying the power from the half bridge to theinstalled fluorescent lamp; a feedback signal generator for supplying afeedback signal indicating an average current passing through the halfbridge; a controller for receiving the feedback signal and in responsethereto adjusting T_(ON); and a memory device for storing a startinglamp type. The controller executes a start-up procedure for theinstalled fluorescent lamp, comprising: retrieving from the memorydevice data indicating the starting lamp type; supplying first andsecond control signals according to the starting lamp type to the firstand second switches to cause the first circuit to warm-up the installedfluorescent lamp during a warm-up period; after the warm-up period,during a test interval supplying the first and second control signals tothe first and second switches to cause the first circuit to supply powerto the installed fluorescent lamp to attempt to overdrive the installedfluorescent lamp; monitoring T_(ON) during the test interval;determining the lamp type of the installed fluorescent lamp based on themonitored T_(ON); and saving in the memory device data indicating thedetermined lamp type of the installed fluorescent lamp as the startinglamp type.

In one embodiment, the installed fluorescent lamp has one of a firstlamp type corresponding to a first, higher, power level, and a secondlamp type corresponding to a second, lower, power level, and thecontroller is further configured to: set a maximum value T_(ON-MAX) forT_(ON) according to the second lamp type; and compare the monitoredT_(ON) to T_(ON-MAX).

According to one optional feature of this embodiment, the controller isfurther configured to determine whether the installed fluorescent lampbelongs to the first lamp type or belongs to the second lamp typedepending on whether the monitored T_(ON) equals T_(ON-MAX) during thetest interval.

Generally, in another aspect, an apparatus comprises: a deviceconfigured to receive an input voltage and in response thereto to supplypower to an installed lamp; and a controller. The controller isconfigured to execute an algorithm comprising: controlling the device tosupply the power to the installed lamp according to a first powercontrol setting that will not overdrive the installed lamp when theinstalled lamp is of a first lamp type and that will overdrive theinstalled lamp when the installed lamp is of a second lamp type,detecting whether the installed lamp is overdriven at the first powercontrol setting; determining the lamp type of the installed lamp basedat least in part on whether the installed lamp is overdriven at thefirst power control setting; and controlling the device to supply thepower to the installed lamp according to the determined lamp type.

In one embodiment, the apparatus also includes a feedback signalgenerator that is configured to provide a feedback signal to thecontroller, and wherein the controller is configured: (1) to compare thefeedback signal to a target value for driving the installed lamp, and(2) to determine whether the installed lamp is overdriven based on aresult of the comparison.

According to one optional feature of this embodiment, the controllerincludes a comparator or amplifier that compares the feedback signalvalue to the target value, and wherein the controller determines thatT_(ON) equals T_(ON-MAX) when an output of the comparator or amplifieris at one of its maximum and minimum values.

In one embodiment, the algorithm also comprises when it is determinedthat the lamp is overdriven at the first power control setting:controlling the device to supply the power to the installed lampaccording to a second power control setting that will not overdrive theinstalled lamp when the installed lamp is of the second lamp type, andthat will overdrive the installed lamp when the installed lamp is of thethird lamp type, detecting whether the installed lamp is overdriven atthe second power control setting; and determining the lamp type of theinstalled lamp based at least in part on whether the installed lamp isoverdriven at the second power control setting.

Generally, in still another aspect a method is provided for supplyingpower to an installed lamp. The method comprises: supplying power to aninstalled lamp according to a first power control setting that will notoverdrive the installed lamp when the installed lamp is of a first lamptype, and that will overdrive the installed lamp when the installed lampis of a second lamp type; detecting whether the lamp is overdriven atthe first power control setting; determining the lamp type of theinstalled lamp based at least in part on whether the installed lamp isoverdriven at the first power control setting; and supplying the powerto the installed lamp according to the determined lamp type.

In one embodiment, the method also includes: comparing a feedback signalto a target value for driving the installed lamp, and determiningwhether the installed lamp is overdriven based on a result of thecomparison.

In one embodiment, the method also includes: selectively turning on andoff first and second switches of a half bridge periodically, whereineach switch has a time T_(ON) in each period where the switch is turnedon, and wherein a power level supplied to the installed lamp varies withT_(ON).

According to one optional feature of this embodiment, the first lamptype corresponds to a first, lower, power level, and the second lamptype corresponds to a second, higher, power level, and the methodcomprises, during a test interval: setting a maximum value T_(ON-MAX)for T_(ON) corresponding to the first lamp type, monitoring TON, andcomparing the monitored T_(ON) to T_(ON-MAX).

According to one optional feature of this embodiment, the method furthercomprises determining whether the installed lamp belongs to the firstlamp type or belongs to the second lamp type depending on whether themonitored T_(ON) equals T_(ON-MAX) during the test interval.

In one embodiment, the method also includes: supplying the power to theinstalled lamp according to a second power control setting that will notoverdrive the installed lamp when the installed lamp is of the secondlamp type, and that will overdrive the installed lamp when the installedlamp is of a third lamp type; detecting whether the lamp is overdrivenat the second power control setting; and determining the lamp type ofthe installed lamp based at least in part on whether the installed lampis overdriven at the second power control setting.

In one embodiment, the first lamp type corresponds to a first, higher,power level lamp, and the second lamp type corresponds to a second,lower, power level lamp.

In one embodiment, the method further comprises saving in a memorydevice data indicating the determined lamp type of the installedfluorescent lamp.

As used herein for purposes of the present disclosure, the term “lamp”should be understood to refer to any one or more of a variety of lightsources, including, but not limited to, fluorescent sources,phosphorescent sources, high-intensity discharge sources (e.g., sodiumvapor, mercury vapor, and metal halide lamps), incandescent sources(e.g., filament lamps, halogen lamps), lasers, LED-based sources, othertypes of electroluminescent sources, pyro-luminescent sources (e.g.,flames), candle-luminescent sources (e.g., gas mantles, carbon arcradiation sources), photo-luminescent sources (e.g., gaseous dischargesources), cathode luminescent sources using electronic satiation,galvano-luminescent sources, crystallo-luminescent sources,kine-luminescent sources, thermo-luminescent sources, tribo luminescentsources, sonoluminescent sources, radio luminescent sources, andluminescent polymers.

A given light source may be configured to generate electromagneticradiation within the visible spectrum, outside the visible spectrum, ora combination of both. Hence, the terms “light” and “radiation” are usedinterchangeably herein. Additionally, a light source may include as anintegral component one or more filters (e.g., color filters), lenses, orother optical components. Also, it should be understood that lightsources may be configured for a variety of applications, including, butnot limited to, indication, display, and/or illumination. An“illumination source” is a light source that is particularly configuredto generate radiation having a sufficient intensity to effectivelyilluminate an interior or exterior space. In this context, “sufficientintensity” refers to sufficient radiant power in the visible spectrumgenerated in the space or environment (the unit “lumens” often isemployed to represent the total light output from a light source in alldirections, in terms of radiant power or “luminous flux”) to provideambient illumination (i.e., light that may be perceived indirectly andthat may be, for example, reflected off of one or more of a variety ofintervening surfaces before being perceived in whole or in part).

The term “lighting unit” is used herein to refer to an apparatusincluding one or more light sources of same or different types. A givenlighting unit may have any one of a variety of mounting arrangements forthe light source(s), enclosure/housing/fixture arrangements and shapes,and/or electrical and mechanical connection configurations.Additionally, a given lighting unit optionally may be associated with(e.g., include, be coupled to and/or packaged together with) variousother components (e.g., control circuitry) relating to the operation ofthe light source(s).

It should be appreciated that all combinations of the foregoing conceptsand additional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the inventive subject matter disclosed herein. In particular, allcombinations of claimed subject matter appearing at the end of thisdisclosure are contemplated as being part of the inventive subjectmatter disclosed herein. It should also be appreciated that terminologyexplicitly employed herein that also may appear in any disclosureincorporated by reference should be accorded a meaning most consistentwith the particular concepts disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention.

FIG. 1 shows a functional block diagram of one embodiment of a lightingunit.

FIG. 2 shows a flowchart of one embodiment of a method of determining atype of lamp that is installed in a lighting unit.

FIG. 3 shows a functional block diagram of relevant portions of oneembodiment of a lighting unit.

FIG. 4 shows some details of relevant portions of one embodiment of alighting unit.

FIG. 5 illustrates the timing of one embodiment of a procedure for alighting unit to determine a lamp type of an installed lamp.

FIGS. 6A-B illustrate example operations of one embodiment of a lamptype determination procedure.

FIGS. 7-10 illustrate experimental results of execution of oneembodiment of a lamp type determination algorithm under four differentsets of conditions.

DETAILED DESCRIPTION

More generally, Applicants have recognized and appreciated that it wouldbe beneficial to provide a device and method that can automaticallydetermine the type of lamp that is currently installed in a lightingunit and select appropriate parameters for supplying power to thedetermined lamp type.

In view of the foregoing, various embodiments and implementations of thepresent invention are directed to a lighting unit, a device forsupplying power to a lamp installed in a lighting unit, a ballast for alamp installed in a lighting unit, and a method of supplying power to alamp installed in a lighting unit, which can determine the type of lampthat is installed in the lighting unit.

FIG. 1 shows a functional block diagram of one embodiment of a lightingunit 1000. Lighting unit 1000 includes an installed lamp 10, which maybe installed in a lighting fixture (not shown) of lighting unit 1000,and an apparatus 1100 for supplying power to installed lamp 10. Lightingunit 1000 also includes a rectifier block 1200, which may furtherinclude a power factor correction (PFC) circuit, a dimming block, andother blocks that operate to convert a standard AC voltage from theelectrical grid to a regulated DC voltage V_(IN) that is supplied toapparatus 1100 of lighting unit 1000. Apparatus 1100 includes a lamppower supply device 1110, a controller 1120, and a feedback signalgenerator 1130, and may be referred to as an electronic ballast. In theembodiment of FIG. 1, controller 1120 receives dimming voltage V_(DIM)which sets the amount of dimming to be applied to lamp 10 by apparatus1100. Feedback signal generator 1130 and controller 1120 operate withlamp power supply device 1110 to form a power control loop for supplyingan appropriate power to lamp 10 according to a desired dimming settingindicated by dimming voltage V_(DIM).

Lighting unit 1000 is capable of employing at least two different typesof lamps as the installed lamp 10, and apparatus 1100 is configuredautomatically to recognize, detect, or determine the type of lamp thatis currently installed in lighting unit as installed lamp 10.

In one embodiment, lighting unit 1000 is configured to employ asinstalled lamp 10 a fluorescent lamp, for example a 4 foot T8fluorescent lamp. In that case, installed lamp 10 may be a 32 watt T8lamp (a first lamp type), or a 28 watt T8 lamp (a second lamp type), ora 25 watt T8 lamp (a third lamp type).

In that case, apparatus 1100 includes a feature wherein it is ableautomatically to detect whether installed lamp 10 is a 32 watt T8 lamp,a 28 watt T8 lamp, or a 25 watt T8 lamp so that it can supply thedesired power level to lamp 10.

FIG. 2 shows a flowchart of one embodiment of a method 2000 ofdetermining a type of lamp that is installed in a lighting unit whichmay be employed by apparatus 1100.

In a first step 2005, a lamp type determination procedure is initiatedby an apparatus.

In some embodiments, a lamp type determination procedure may beinitiated each time that a lighting unit is powered on. In someembodiments, a lamp type determination procedure may be initiatedwhenever an apparatus determines that a lamp has been replaced. In thatcase, for example, the apparatus may detect when it is driving an openload because a lamp has been removed, and then detect when the load ispresent again because a new lamp has been installed, and the apparatusmay initiate the lamp type determination procedure upon detecting thatthe load is again present. Other criteria may be employed for initiatinga lamp type determination procedure.

In a step 2010, an apparatus retrieves from a memory device stored lamptype data indicating a starting lamp type. The starting lamp type is alamp type that is used as a starting point for the lamp determinationprocedure. In some embodiments, the stored lamp type data may correspondto a default lamp type stored into the memory device at the factory whenthe apparatus is manufactured. In some embodiments, the stored lamp typedata may correspond to a lamp type that was detected by the apparatusthe last time the apparatus was powered on. In some embodiments, thestored lamp type data may correspond to a lamp type that was lastdetected by the apparatus prior to detecting that a new lamp has beeninstalled. The lamp type data may be any kind of data, including forexample an ID code that may be used by an apparatus to identify the typeof lamp that should be used by the lamp determination procedure as thestarting lamp type.

In a step 2015, the installed lamp(s) is/are warmed up using powercontrol settings for the starting lamp type.

In a step 2020, the apparatus tries to overdrive the installed lamp(s)during a test interval using first power control setting(s). Exampleembodiments of trying to overdrive an installed lamp will be describedin greater detail below.

In a step 2025, the apparatus determines whether or not the installedlamp(s) is/are overdriven. Example embodiments of determining whether ornot installed lamp(s) is/are overdriven will be described in greaterdetail below. If it is determined in step 2025 that installed lamp(s)is/are not overdriven, then in a step 2030 it is determined that theinstalled lamp(s) is/are of a first, higher power lamp type, for examplea 32 W T8 lamp type. Then in a step 2035 the apparatus drives the lampaccording to the first lamp type. Beneficially, data indicating thefirst lamp type is also stored in the memory device as the starting lamptype, and the procedure ends.

If it is determined in step 2025 that the installed lamp(s) is/areoverdriven, then in a step 2040 the apparatus tries to overdrive theinstalled lamp(s) during a test interval using second power controlsetting(s).

In a step 2045, the apparatus determines whether or not the installedlamp(s) is/are overdriven. If it is determined in step 2045 thatinstalled lamp(s) is/are not overdriven, then in a step 2050 it isdetermined that the installed lamp(s) is/are of a second, lower powerlamp type, for example a 28 W T8 lamp type. Then in a step 2055 theapparatus drives the lamp according to the second lamp type.Beneficially, data indicating the second lamp type is stored in thememory device as the starting lamp type, and the procedure ends.

If it is determined in step 2045 that the installed lamp(s) is/areoverdriven, then in a step 2060 it is determined that the lamp(s) is/areof a third, even lower power lamp type, for example a 25 W T8 lamp type.In a step 2065 the apparatus drives the lamp according to the third lamptype. Beneficially, data indicating the third lamp type is stored in thememory device as the starting lamp type, and the procedure ends.

In some embodiments where only two lamp types are contemplated, thensteps 2040, 2045, 2060 and 2065 may be omitted, and when the installedlamp(s) is/are not overdriven in step 2025, it is determined that theinstalled lamp(s) is/are of a second, lower power lamp type, for examplea 28 W T8 lamp type. Alternatively, in some embodiments where more thanthree lamp types are contemplated, steps similar to 2020-2035 or2040-2055 may be repeated for each additional lamp type.

In method 2000, the apparatus begins testing for overdrive at thehighest power level and if overdrive is detected, it then “works its waydown” by testing at the next highest power level below that, and thenthe next power level below that, etc. until if finds a level that doesnot overdrive the lamp(s). However, in alternative embodiments, theapparatus may begin by testing at the lowest power level and ifoverdrive is detected, it then “works its way up” by testing at the nextpower level above that, and then the next power level above that, etc.until if finds a level that does overdrive the lamp(s). Otherarrangements are also possible.

Although to provide a clear and concrete illustration, the exampleembodiment of FIG. 2 was described above in terms of fluorescent lamps,and in particular fluorescent T8 lamps, it should be understood that theillustrated method could be applied where appropriate to determining aninstalled lamp type for lamps employing other technologies.

In various embodiments, one or more of the following features may beapplied to the method of FIG. 2: the warm-up procedure may always beexecuted at a high output level (rather than using the level for thestarting lamp type stored in memory); and when changing T_(ON) in orderto overdrive, visibility may be decreased by using a slow change(sweep).

Also in some cases where a lamp is replaced while a deep dimming levelis applied to the lighting unit, the method 2000 may become visible to auser because it involves applying a high power level to the lamp(s) totry to overdrive it/them. Accordingly, so that the overdriving test isnot visible to a user, in some embodiments in step 2005 afterreplacement of a lamp is detected, the lamp determination procedure mayonly be initiated once the amount of dimming is set to be very low(i.e., the lamp(s) have maximum or near maximum light output level).This has the side effect that the lighting unit may be set at the wrongpower setting after replacing the lamp(s) until the light level is sethigh enough for the lamp determination procedure to be initiated.

FIG. 3 shows a functional block diagram of relevant portions of oneembodiment of a lighting unit 3000. Lighting unit 3000 includes aninstalled lamp 10, which may be installed in a lighting fixture (notshown) of lighting unit 3000, and an apparatus 3100 for supplying powerto installed lamp 10. Apparatus 3100 includes a lamp power supply device3110, a controller 3120, and a feedback signal generator 3130, and maybe referred to as an electronic ballast. Power supply device 3110includes a half-bridge 3112, a resonant circuit 3114, and a feedbacksignal generator 3130. Controller 3120 includes a processor (e.g., amicroprocessor) 3122, a memory device 3124, comparator or amplifier3126, and other signal processing components.

In operation, half bridge 3112 receives a voltage V_(IN), which may be aregulated and power factor corrected DC voltage, and supplies power toinstalled lamp 10 via resonant circuit 3114. Controller 3120 receives adimming control signal V_(IN) and regulates a power supplied by lamppower supply device 3110 to installed lamp 10 to achieve a correspondinglevel of dimming. In some embodiments, controller 3120 controls thepower supplied from lamp power supply device 3110 to installed lamp 10by adjusting a frequency of a signal output by half-bridge 3112 toresonant circuit 3114. In some embodiments, as the frequency of thesignal output by half-bridge 3112 to resonant circuit 3114 is decreased,the power delivered by lamp power supply device 3110 to lamp 10 isincreased.

In some embodiments, half bridge 3112 includes first and second switches(e.g., transistors) having first and second switches that areselectively turned on and off periodically in response to controlsignals 3015 and 3025 provided by controller 3120, wherein each switchhas a time T_(ON) in each period where the switch is turned whereby thepower level supplied to the installed lamp 10 varies with T_(ON).

Feedback signal generator 3130 provides a feedback signal 3035 tocontroller 3120 to create a power control loop that permits controller3130 to control operation of lamp power supply device 3110 to supply adesired power level to installed lamp 10. In one embodiment, thefeedback signal indicates an average current level flowing through halfbridge 3112. When V_(IN) is a constant DC voltage, then by regulatingthe average current through half bridge 3112 controller 3130 canregulate the power supplied to installed lamp 10.

Accordingly, in some embodiments controller 3130 periodically (e.g.,once every 850 μsec measurement cycle) measures the average currentthrough half bridge 3112 and in response thereto adjusts the “ON” timeT_(ON) to regulate the power supplied to installed lamp 10. That is, insome embodiments, during each measurement cycle controller 3130 will notchange T_(ON), but at the end of the cycle controller 3130 will changeT_(ON) for the next cycle based on the half bridge current measurementfrom the previous cycle to correct and maintain regulation of the powersupplied to installed lamp 10.

Lighting unit 3000 is capable of employing at least two different typesof lamps as the installed lamp 10, and apparatus 3100 is configuredautomatically to recognize, detect, or determine the type of lamp thatis currently installed in lighting unit as installed lamp 10.

In some embodiments, lighting unit 3000 is configured to employ asinstalled lamp 10 a fluorescent lamp, in particular a T8 fluorescentlamp. In that case, installed lamp 10 may be a 32 watt T8 lamp (a firstlamp type), or a 28 watt T8 lamp (a second lamp type), or a 25 watt T8lamp (a third lamp type).

In that case, apparatus 3100 includes a feature wherein it is ableautomatically to detect whether installed lamp 10 is a 32 watt T8 lamp,a 28 watt T8 lamp, or a 25 watt T8 lamp.

In one example embodiment, controller 3130 has information indicatingthe current value of T_(ON) at all times. By definition, T_(ON-MAX) isthe maximum permissible value of T_(ON) for the power control settingfor a given installed lamp 10, and this value should not be reachedduring normal operations of lighting unit 3000 with installed lamp 10.When lamp power supply device 3110 is not able to satisfy its targetpower requirements, then controller 3130 will set T_(ON) to T_(ON-MAX).

Beneficially, this is exactly the situation that occurs when a lowerpower lamp (e.g., a 28 watt T8 lamp) is installed and driven at a higherpower regulation set point (e.g., at a first power control setting for a32 watt T8 lamp). In such a case, having T_(ON) at T_(ON-MAX) is definedas an overdriving condition.

Accordingly, apparatus 3100 may execute a method of detecting a lamptype of installed lamp 10, such as the method 2000. In that case, instep 2010 controller 3120 retrieves data indicating a starting lamp typefrom the memory device, and in step 2015 apparatus 3100 warms upinstalled lamp 10 using settings for the starting lamp type. Then instep 2020 apparatus 3100 attempts during a test interval to overdriveinstalled lamp 10 by employing a power control setting that will notoverdrive installed lamp 10 and therefore will not cause T_(ON) to reachat T_(ON-MAX) when installed lamp 10 belongs to a first lamp type (e.g.,a 32 W lamp type) intended to operated at a higher power level, but thatwill overdrive installed lamp 10 and will cause T_(ON) to reachT_(ON-MAX) when installed lamp 10 belongs to a second lamp type (e.g., a28 W lamp type) intended to operated at a lower power level. In step2025 controller 3120 detects whether or not installed lamp 10 isoverdriven by determining whether, during the test interval, T_(ON)reaches T_(ON-MAX). In some embodiments, overdriving may be defined ashaving T_(ON)=T_(ON-MAX) for a percentage of the test interval, andT_(ON) does not have to equal T_(ON-MAX) for 100% of the test interval.Consequently not detecting overdriving may be defined as not havingT_(ON)=T_(ON-MAX) for a certain percentage of time during the testinterval.

Based at least in part on whether it is determined that installed lamp10 is overdriven at the first power control setting, controller 3120determines the lamp type of installed lamp 10. In particular, when onlytwo lamp types (e.g., 32 W and 28 W) are contemplated, then a finaldecision as to which lamp type is installed may be made once it isdetermined whether installed lamp 10 is overdriven at the first powercontrol setting. In another case where three lamp types (e.g., 32 W, 28W, and 25 W) are contemplated, then if installed lamp 10 is overdrivenat the first power control setting, it is necessary to repeat theprocedure at a second power control setting that will not overdriveinstalled lamp 10 and therefore will not cause T_(ON) to reach atT_(ON-MAX) when installed lamp 10 belongs to the second lamp type (e.g.,a 28 W lamp type), but that will overdrive installed lamp 10 and willcause T_(ON) to reach T_(ON-MAX) when installed lamp 10 belongs to thethird lamp type (e.g., a 25 W lamp type) intended to operated at an evenlower power level, such as described above with respect to steps2040-2065 of FIG. 2. As before, depending on the number of lamp typesthat are contemplated, this procedure may be repeated as necessary. Asmentioned earlier, a different embodiment of the procedure may beemployed, for example, by beginning testing at the lowest power leveland if overdrive is detected, then testing at the next power level abovethat, and then the next power level above that, etc. until if finds alevel that does overdrive the lamp(s).

In some embodiments, once the installed lamp type is determined,controller 3120 may write data indicating the installed lamp type intomemory device 3124 as the new starting lamp type.

In some embodiments, the feedback signal reflecting the current throughhalf bridge 3112 may be supplied to a comparator or amplifier 3126 andcompared to a reference value corresponding to a desired power level tobe applied to installed lamp 10 (for example, a dimmed levelcorresponding to V_(DIM)) in order to generate the appropriate T_(ON)for the control signal(s) for controlling the power supplied by lamppower supply device 3110 to installed lamp 10. In that case, controller3120 may determine whether or not T_(ON)=T_(ON-MAX) and installed lamp10 is overdriven by monitoring whether or not the output of comparatoror amplifier 3126 goes “open loop” and is at its maximum (or minimum)“rail” value due to overdriving a lower power lamp. In some embodiments,processor 3122 may just measure T_(ON) directly. Based on whetherT_(ON)=T_(ON-MAX), indicating overdriving, controller 3120 can changethe reference value provided to the amplifier or comparator 3126 toproperly drive installed lamp 10.

FIG. 4 shows some details of relevant portions of one embodiment of alighting unit 4000. Lighting unit 4000 includes an installed lamp 10,which may be installed in a lighting fixture (not shown) of lightingunit 4000, and an apparatus 4100 for supplying power to installed lamp10. Apparatus 4100 includes a lamp power supply device and feedbacksignal generator 4140, and a controller 4120. Lamp power supply deviceand feedback signal generator 4140 includes a half-bridge includingfirst and second switching devices (e.g., field effect transistors) 4112a and 4112 b, a resonant circuit 4114, and a feedback signal generator4130.

An operation of lighting unit 4000 is the same as lighting unit 3000 andtherefore will not be repeated here.

In one embodiment, a lighting unit may operate according to theparameters shown in Table 1 below.

TABLE 1 parameter value description POST_IGNITION_LAMP_REC_DELAY_TIME  1[sec] Earliest time after ignition when lamp recognition procedure maystart LAMP_RECOGNITION_WARM_UP_TIME  60 [sec] Warm-up time before theoverdriving test LAMP_RECOGNITION_DO_TIME 100 [msec] Overdriving testduration LAMP_RECOGNITION_SWEEP_TIME 500 [msec] Time to move tooverdriving wattage or return from it if needed LAMP_RECOGNITION_LEVEL 94 [%] Minimum output light level suitable for warm- up (100% isfull-on) LAMP_RECOGNITION_OVERDRIVE_RATIO  50 [%] Percentage of timeduring the overdriving test sufficient for positive result.

FIG. 5 illustrates the timing of one embodiment of a procedure for alighting unit to determine a lamp type of an installed lamp, showing alight level as a function of time during a start-up or power-onprocedure, including a warm-up period and a test interval.

FIGS. 6A-B illustrate example operations of one embodiment of a lamptype determination procedure where it is contemplated that a lightingunit may operate with two different lamp types: a 32 W lamp and a 28 Wlamp. FIGS. 6A-B illustrate four different possible cases for lamprecognition, according to the starting lamp type stored in memory andemployed for start-up and the lamp type of the actual installed lamp, asillustrated in Table 2 below.

TABLE 2 Starting lamp type Installed lamp(s) [W] [W] 28 28 28 32 32 2832 32

FIG. 6A illustrates the two cases where the starting lamp type is 28 Wand therefore the lighting unit starts up as if the lamp type of theinstalled lamp(s) is 28 W. In the first case (top trace at right), theinstalled lamp is a 32 W lamp, and in the second case (bottom trace atright), the installed lamp is a 28 W lamp. FIG. 6BA illustrates the twocases where the starting lamp type is 32 W and therefore the lightingunit starts up as if the lamp type of the installed lamp(s) is 32 W. Inthe first case (bottom trace at right), the installed lamp is a 28 Wlamp, and in the second case (top trace at right), the installed lamp isa 32 W lamp.

FIGS. 7-10 illustrate experimental results of execution of oneembodiment of a lamp type determination algorithm under four differentsets of conditions. Each of the FIGS. 7-10 shows a top trace and abottom trace, wherein the top and bottom traces show the same signals atdifferent time scales, the bottom trace having a time trace that is anexploded view around the time enclosed within the rectangular box drawnon the top trace.

FIG. 7 illustrates a case where the lighting unit has a starting lamptype for a 28 W lamp, and the actual installed lamp is a 28 W lamp.Here, the top trace has a time scale of 500 msec. /division, and thebottom time trace has a time scale of 200 msec. /division. As shown inFIG. 7, after a warm up period of about 1 minute wherein the installedlamp is warmed up in accordance with a warm up setting for a 28 W lamp,the lighting unit attempts to overdrive the installed lamp during a testinterval for determining a lamp type for the installed lamp. Inparticular, power is supplied to the installed lamp according to a firstpower control setting that will not overdrive the installed lamp whenthe installed lamp is a 32 W lamp, but that will overdrive the installedlamp when the installed lamp is a 28 W lamp. In this case, an overdrivecondition is detected, and so the lamp is determined to be a 28 W lamp,and is thereafter driven using a power control setting (e.g., T_(ON))for a 28 W lamp.

FIG. 8 illustrates a case where the lighting unit has a starting lamptype for a 28 W lamp, and the actual installed lamp is a 32 W lamp.Here, the top trace has a time scale of 500 msec. /division, and thebottom time trace has a time scale of 200 msec. /division. As shown inFIG. 8, after a warm up period of about 1 minute wherein the installedlamp is warmed up in accordance with a warm up setting for a 28 W lamp,the lighting unit attempts to overdrive the installed lamp during a testinterval for determining a lamp type for the installed lamp. Inparticular, power is supplied to the installed lamp according to a firstpower control setting that will not overdrive the installed lamp whenthe installed lamp is a 32 W lamp, but that will overdrive the installedlamp when the installed lamp is a 28 W lamp. In this case, an overdrivecondition is not detected, and so the lamp is determined to be a 32 Wlamp, and is thereafter driven using a power control setting (e.g.,T_(ON)) for a 32 W lamp. Furthermore, the starting lamp type may beupdated to reflect a 32 W lamp.

FIG. 9 illustrates a case where the lighting unit has a starting lamptype for a 32 W lamp, and the actual installed lamp is a 28 W lamp.Here, the top trace has a time scale of 500 msec. /division, and thebottom time trace has a time scale of 50 msec. /division. As shown inFIG. 9, after a warm up period of about 1 minute wherein the installedlamp is warmed up in accordance with a warm up setting for a 32 W lamp,the lighting unit attempts to overdrive the installed lamp during a testinterval for determining a lamp type for the installed lamp. Inparticular, power is supplied to the installed lamp according to a firstpower control setting that will not overdrive the installed lamp whenthe installed lamp is a 32 W lamp, but that will overdrive the installedlamp when the installed lamp is a 28 W lamp. In this case, an overdrivecondition is detected, and so the lamp is determined to be a 28 W lamp,and is thereafter driven using a power control setting (e.g., T_(ON))for a 28 W lamp. Furthermore, the starting lamp type may be updated toreflect a 28 W lamp.

FIG. 10 illustrates a case where the lighting unit has a starting lamptype for a 32 W lamp, and the actual installed lamp is a 32 W lamp.Here, the top trace has a time scale of 500 msec. /division, and thebottom time trace has a time scale of 200 msec. /division. As shown inFIG. 10, after a warm up period of about 1 minute wherein the installedlamp is warmed up in accordance with a warm up setting for a 32 W lamp,then the lighting unit attempts to overdrive the installed lamp during atest interval for determining a lamp type for the installed lamp. Inparticular, power is supplied to the installed lamp according to a firstpower control setting that will not overdrive the installed lamp whenthe installed lamp is a 32 W lamp, but that will overdrive the installedlamp when the installed lamp is a 28 W lamp. In this case, an overdrivecondition is not detected, and so the lamp is determined to be a 32 Wlamp, and is thereafter driven using a power control setting (e.g.,T_(ON)) for a 32 W lamp.

While several inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of or “exactly one of,” or, when used inthe claims, “consisting of,” will refer to the inclusion of exactly oneelement of a number or list of elements. In general, the term “or” asused herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of and “consistingessentially of shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

1. A device for supplying power to an installed fluorescent lamp, thedevice comprising: a first circuit for receiving an input voltage(V_(IN)) and in response thereto supplying power to the installedfluorescent lamp, the first circuit including: a half bridge havingfirst and second switches that are selectively turned on and offperiodically, wherein each switch has a time T_(ON) in each period wherethe switch is turned on, and wherein the power level supplied to theinstalled fluorescent lamp varies with T_(ON), and a resonant circuitfor supplying the power from the half bridge to the installedfluorescent lamp; a feedback signal generator for supplying a feedbacksignal indicating an average current passing through the half bridge; acontroller for receiving the feedback signal and in response theretoadjusting T_(ON); and a memory device for storing a starting lamp type,wherein the controller executes a lamp type determination procedure forthe installed fluorescent lamp, comprising: retrieving from the memorydevice data indicating the starting lamp type; supplying first andsecond control signals according to the starting lamp type to the firstand second switches to cause the first circuit to warm-up the installedfluorescent lamp during a warm-up period; after the warm-up period,during a test interval supplying the first and second control signals tothe first and second switches to cause the first circuit to supply powerto the installed fluorescent lamp to attempt to overdrive the installedfluorescent lamp; monitoring T_(ON) during the test interval;determining the lamp type of the installed fluorescent lamp based on themonitored T_(ON); and saving in the memory device data indicating thedetermined lamp type of the installed fluorescent lamp as the startinglamp type.
 2. The device of claim 1, wherein the installed fluorescentlamp has one of a first lamp type corresponding to a first, higher,power level, and a second lamp type corresponding to a second, lower,power level, and wherein the controller sets a maximum value T_(ON-MAX)for T_(ON) during the test interval corresponding to the first lamptype, and compares the monitored T_(ON) to T_(ON-MAX).
 3. The device ofclaim 2, wherein the controller determines whether the installedfluorescent lamp belongs to the first lamp type or belongs to the secondlamp type depending on whether the monitored T_(ON) equals T_(ON-MAX)during the test interval.
 4. The device of claim 2, wherein thecontroller sets a threshold percentage, and determines whether theinstalled fluorescent lamp belongs to the first lamp type or belongs tothe second lamp type depending on whether the monitored T_(ON) equalsT_(ON-MAX) for at least the threshold percentage of time during the testinterval.
 5. The device of claim 2, wherein the feedback signal has avalue, and wherein the controller compares the feedback signal value toa target value and in response thereto adjusts T_(ON) to attempt tocause the feedback signal value to equal the target value.
 6. The deviceof claim 5, wherein the target value is selected according to one of thefirst and second lamp types.
 7. The device of claim 6, wherein thecontroller includes a comparator or amplifier that compares the feedbacksignal value to the target value, and wherein the controller determinesthat T_(ON) equals T_(ON-MAX) when an output of the comparator oramplifier is at one of its maximum and minimum values.
 8. The device ofclaim 6, wherein the controller includes a processor that measuresT_(ON).
 9. (canceled)
 10. (canceled)
 11. (canceled)
 12. (canceled) 13.(canceled)
 14. (canceled)
 15. A method, comprising: supplying power toan installed lamp according to a first power control setting that willnot overdrive the installed lamp when the installed lamp is of a firstlamp type, and that will overdrive the installed lamp when the installedlamp is of a second lamp type and includes selectively turning on andoff first and second switches of a half bridge periodically, whereineach switch has a time T_(ON) in each period where the switch is turnedon, and wherein a power level supplied to the installed lamp varies withT_(ON); detecting whether the installed lamp is overdriven at the firstpower control setting; determining the lamp type of the installed lampbased at least in part on whether the installed lamp is overdriven atthe first power control setting; and supplying the power to theinstalled lamp according to the determined lamp type, wherein the firstlamp type corresponds to a first, lower, power level, and the secondlamp type corresponds to a second, higher, power level, and the methodcomprises, during a test interval; setting a maximum value T_(ON-MAX)for T_(ON) corresponding to the first lamp type, monitoring T_(ON), andcomparing the monitored T_(ON) to T_(ON-MAX);
 16. The method of claim15, further comprising comparing a feedback signal to a target value fordriving the installed lamp, and determining whether the installed lampis overdriven based on a result of the comparison.
 17. (canceled) 18.(canceled)
 19. The method of claim 15, further comprising determiningwhether the installed lamp belongs to the first lamp type or belongs tothe second lamp type depending on whether the monitored T_(ON) equalsT_(ON-MAX) during the test interval.
 20. The method of claim 15, furthercomprising: supplying the power to the installed lamp according to asecond power control setting that will not overdrive the installed lampwhen the installed lamp is of the second lamp type, and that willoverdrive the installed lamp when the installed lamp is of a third lamptype; detecting whether the installed lamp is overdriven at the secondpower control setting; and determining the lamp type of the installedlamp based at least in part on whether the installed lamp is overdrivenat the second power control setting.
 21. The method of claim 15, whereinthe first lamp type corresponds to a first, higher, power level lamp,and the second lamp type corresponds to a second, lower, power levellamp.
 22. The method of claim 15, further comprising saving in a memorydevice data indicating the determined lamp type of the installed lamp.